1. Field of the Invention
The present invention relates to a defect inspection of an object such as a mask or a reticle of a semiconductor wafer. More particularly, the invention relates to a method and apparatus for inspecting an auxiliary pattern (e.g., OPC: optical proximity correction pattern) formed on a mask or the like in order to enhance the resolution at the time of light exposure.
Further, the invention relates to a method and apparatus for inspecting a mask, a reticle, a semiconductor wafer, a semiconductor chip and a semiconductor circuit in which a pattern related to semiconductor production is formed, or a sample such as a printed substrate, a liquid crystal display substrate. More particularly, the invention relates to a method and apparatus for inspecting a pattern to find defects, therein, dust thereon and the like.
2. Discussion of the Background
In a step of manufacturing a semiconductor device, for example, an exposure apparatus performs exposure on the semiconductor substrate, by using a mask or a reticle. The circuit pattern transferred to the semiconductor substrate becomes smaller year by year. Due to the limited resolution of the exposure apparatus, the circuit pattern transferred to the substrate has rounded corners and edges as is illustrated in FIG. 1.
To perform exposure to provide on the substrate a pattern which is identical to the design pattern, an auxiliary pattern is now made in a mask or the like, as is shown in FIG. 2.
A mask having an auxiliary pattern is inspected. More specifically, the data representing the real pattern obtained by photographing the auxiliary pattern is compared with the data representing the design pattern, thereby to determine whether the pattern has defects or not.
Circuit patterns are made smaller and smaller as described above, and the resolution of the real pattern obtained by photographing of the circuit pattern is approaching the width of each element of the real pattern. In other words, the pattern precision is increasing. Thus, in a method in which differential is effected to detect the direction of a corner or an edge and real pattern data and design pattern data are compared, the position shift may occur between real pattern data and the design data. This inevitably lowers the accuracy of pattern inspection.